Process for improving lead-alloy articles



Patented June 2%, 1928..

unit-an aram e V aerate? tartar crates.

BEGINAIJ) SCOTT DEAN AND WILLIAM- EWART HUDSON, 0E OAK PARK, ILLINOIS, AS-

SIGNORS T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N, K,

A CORPORATION OF NEW YORK.

'raoonss roa mraovmie LEAD-ALLOY aa'rroLas.

No Drawing. Application filed February This invention relates to a process for improving lead alloy articles, particularly lead alloy articles on which work has been performed.

An object of this invention is to provide a process for improving articles which have been formed from certain lead alloys.

A further object of this invention is to provide a that the process of improving and forming may be carried out substantially at the same time.

A further object of this invention is to provide a process for forming articles from a hardened sheet of lead alloy.

The process may be used to advantagein the manufacture of various products made of an improved lead alloy and particularly in the manufacture of storage battery plates and improved lead alloy tape.

Heretofore articles formed from lead or lead alloys have been insusceptible to hardcning except by ter. which would/have the effect of forming with the lead an alloy which would be somewhat harder than the lead.: A process has been worked out which makes possible a considerable hardening and improving of lead by the addition of a small percentage of antimony or other alloying element, such as tin, and a subsequent heat treatment. For a full disclosure of the details of this treatment, reference is made to our co-pending application, Serial No. 690,716, filedFebruary 5, 1924.- I

It is suflicientto state here, briefly, that this heat treatment consists in adding to lead, matter the solubility of which in lead varies with temperature, reducing the resulting alloy to a solid solution forming a supersaturated solid solution, and allowing the alloy to assume a more stable state. One process for accomplishing these objects is described in our application above referred to, which process consists briefly in heating, quenching and aging the alloy.

This invention is based on the discovery that the formation of a lead alloy solid solution can be brought about more quickly when work is performed upon the alloy article, thereby greatly reducing the time required in the heating step of the process described in the application referred to process for so forming lead alloys the simple addition of mat- I 5, 1924. Serial No, 690,719.

work which-is performed. upon the alloy has the effect of breaking down the structural formation of the mass and reducing it to such a state that the solution takes place very quickly. A lead alloy article if heated to a temperature required to obtain a solid solution of the particular elements present may "be reduced to a homogeneous solid solution almost instantaneously by any work violent enough to cause deformation of the crystalline structure. In the case, for instance, of an alloy having approximately 2% per cent antimony to 97 per cent lead, heated to a temperature of 240 C. and rolled or struck with a machine hammer or punch or other forming tool, solid solution is formed quickly enough so that immediately after the work has been completed, the article may be quenched in any convenient way to atemperature below 100 C. After this quenching, aging at room temperature or at temperatures below 100 C. will cause a very great hardening and improvement of the alloy. 4

In our co-pending application referred to above it is shown that the time of heating required for a cast lead antimony article of 2.25% antimony content is about seventytwo hours. As noted also in this application work performed upon the lead antimony article tends to hasten the forming of solution. All other variables i. e. temperature, percentage of solute and the like, being equal the time of heating is cut down, proportionally to the work performed. When a very great amount of work is exerted on the alloy a substantially solid solution can sometimes be formed in only a few minutes.

The type of work may vary, and the results remain substantially the same.

The method constituting the present invention may be employed to advantage where antimony is used as the alloying element and the article formed from the alloy is stamped out cold, or if it is stamped out hot must be allowed to cool for some reason. This formed article in its cold state may be heated up to the temperature which would be required for the antimony present to enter solution. It will be found that only a I articles which have been formed for two or three years may be hardened under this method in a very short length of time, providing said article has, during this period, remained at a temperature below the temperature of recrystallization of the alloy constituents, believed in lead antimony alloys of the'type employed to be about 100 C. If this article has, during this period of time, been at a higher temperature, so as to permit recrystallization, the time required for heating must be considerably lengthened.

A suitable illustrative process which can be adapted to the manufacture'of articles which can be formed by rolling is as follows The proper proportions of lead and alloying element may be cast in the form of an ingot and-heated to atemperature slightly below the fusing temperature. The ingot is then rolled into the form required and kept h-otduring this rolling process. Upon coming out of the rolls it is quenched and aged at room temperature. Such a process can be applied to the manufacture of lead allo tape and similar articles.

As a urther illustration'a process to be used for forming lead alloy articles such as storage battery grids by means of stamping machinery, may be carried on in the following manner:

The lead alloy is cast into the form of .an 'ingot and /heated when solid to a temperature of about 240 C. It is then introduced hot into a set of rolls where it is rolled into the form of a flat sheet. This fiat sheet is introduced hot under the stamping machinery and the form required stamped therefrom. The formed article is then quenched and aged at room temperature.

Such a process for forming lead alloy articles by means of stamping machinery and the like may also be carried on as follows:

The lead alloy is cast in requisite proportions in the form of a slug or ingot. The

said ingot is then heated to a temperature aging at room temperature. Either before or after the sheet has attained maximum hardness the desired forms may be stamped therefrom. lVhatever the type of work employed the article may be quenched immediately after the formin of the solid solution. If the work 'at the big temperature has not been suflicient to form the solution, additional heating will be required before the article is quenched.

,lVhat is claimed is:

1. A process for producing improved formed articles composed of a lead-antimony alloy, which consists in casting a lead-antimony ingot with an antimony content up to three per cent, rolling said ingot at a temper ature below 245 C. to form a solid solution of the alloy and to work the ingot into the shape required, quenching said rolled article to a temperature below 100 C. to produce a supersaturated solid solution, and aging at a temperature below 100 C.

2. A process for producing improved formed articles composed of a lead-antimony alloy, which consists in casting the lead-antimony alloy in the form of an ingot, rolling said ingot while hot toform a solid solution of the alloy and to shape the ingot into a sheet, stamping said article from the sheet, quenching to a temperature below 100 C. to produce a supersaturated solidsolution, and aging at atemperature below 100 C.

In 'witness whereof, we hereunto subscribe our names this 22nd day of January A. D, 1924:.

REGINALD soo'rr DEAN. 7 WILLIAM swam HUDSON. 

